Predictors of Medication Adherence and Antiretroviral Resistance Among HIV-Infected Cocaine Abusers Although Highly Active Antiretroviral Therapy (HAART) has been shown to dramatically reduce morbidity and mortality among HIV- infected individuals, without rigorous medication adherence viral replication will ensue and antiretroviral resistant HIV mutations will arise. Among HIV+ patients, there is growing evidence that those especially likely to demonstrate poor adherence are those who evidence significant neuropsychological impairment and those who are cocaine abusing/dependent. Using a structural equation modeling approach, the proposed study will investigate the impact of cocaine abuse, neurocognitive dysfunction, psychiatric disorder, psychosocial factors, demographic characteristics, and medication regimen complexity on medication adherence in a multiethnic sample of HIV+ cocaine abusing patients. Adherence will be objectively determined by use of computerized Medication Event Monitoring System (MEMS) caps, pill counts, adherence questionnaires, and self-report. Specific aims include: (1) how cocaine abuse/dependence affects medication adherence in HIV+ individuals, and how this interacts with time other variables of interest; (2) whether cocaine abuse and pattern of adherence failure are associated with the development of antiretroviral resistant HIV mutations, as indexed through genotypic resistance assays; (3) the predictive relationship between medication adherence and factors such as neurocognition, psychiatric status, risk taking, medical decision making and other critical psychosocial and sociocultural factors; and (4) the development of a taxonomy of risk factors and protective factors that will reliably identify subtypes of adherers/non-aderers. These questions will be investigated by our multidisciplinary team in a diverse sample of 300 HIV+ cocaine abusing/dependent adults. A comprehensive battery of psychosocial measures and neuropsychological tests will be administered at baseline and subjects adherence to their prescribed medical regimen will be monitored on a monthly basis for 6 months with the MEMS caps methodology. A blood sample will also be taken at baseline and at study completion, and assayed to determine whether antiretroviral resistant HIV mutations develop. It is expected that results from this study will help to identify those dually diagnosed HIV+ patients that are especially likely to be non- adherent and to inform targets for interventions that will enhance treatment adherence in this high risk population.